Willian says Chelsea have no margin for error if the reigning champions are to maintain their Premier League title challenge at West Ham United this weekend.
Antonio Conte's side fell short in their bid to wrap up the opening stage of their Champions League campaign as group winners following a 1-1 draw with Atletico Madrid.
The failure to beat the Spanish side means they risk drawing Barcelona or Paris Saint-Germain in the knockout stages of the competition.
Chelsea boss Conte, though, will be anxious his players forget about the European campaign that is now on hold until the New Year, and set about the task of closing the eleven-point gap to Premier League leaders Manchester City.
Saturday's trip to the London Stadium marks the opening game in this weekend’s round of fixtures and a Chelsea victory would lay down a marker before City meet second-placed United in the Manchester derby the following day.
With Pep Guardiola's side showing no sign of faltering, Chelsea midfielder Willian is well aware the pressure is on Conte's team to avoid any slip-ups.
"We have to win," the Brazilian told the London Evening Standard. "We are playing away. Of course, it's going to be a difficult game. But I think we can get the three points."
- No comfort zone -
Alvaro Morata will shoulder responsibility for leading Chelsea's attack and try to extend a scoring run that has brought three goals in his past five Premier League games.
Morata, 25, who has settled well at Stamford Bridge, says he has no regrets about leaving Real Madrid in the summer transfer window and credits Conte with helping him improve as a player.
"Antonio Conte helps you to grow because you can never get too comfortable or find a comfort zone," he told the Evening Standard. "He wants every single one of us to give our maximum.
"Last year I wasn't playing often. Now in every game there's a real chance of playing -- if you train well you are going to play."
Conte will select from a position of strength against West Ham, with centre-back David Luiz the only player expected to be sidelined with injury.
The Italian was given a clear warning his side cannot expect an easy ride against the Hammers during the east London side's trip to Manchester City last weekend when they lost out to a late goal.
David Moyes believes he has made progress in the four games since he succeeded Slaven Bilic, even though the club is still mired in the relegation zone.
Adrian, who replaced Joe Hart at City because the England keeper was ineligible to face his former club, said: "We made things difficult for City. I think we should continue with the line of defending well and looking dangerous when attacking.
"It is clear that we have a difficult streak against teams from the top of the table but it is also clear that all Premier League matches are difficult. We have to always play with the same mentality, to get points and go match-by-match."
Moyes must decide whether to recall Hart and is hoping Winston Reid will be fit enough to return in central defence.